Summary The broad goal of this project is to develop a suite of chemistry-driven tools to study the detailed mechanism by which histone mutations associated with cancers dys-regulate chromatin states, leading to disease. We will focus our efforts on a set of H3 mutants linked to pediatric gliomas (H3K27M and H3G34R/V) and chondroblastomas (H3K36M). By combining the use of chemically-defined chromatin templates with biochemical, proteomic and genomic approaches, we seek to develop a sufficient body of knowledge around the H3 mutants such that logical paths to therapy can be conceived. As an example of this, we will explore the idea that the toxic effect of these mutants on methyltransferase activities can be neutralized by manipulation of other epigenetic modification pathways. We imagine that many of the technologies developed in the context of this project will have broad utility in the epigenetics field generally.